Electrical musical instrument



June 22, 1965 Filed- Nov. 15, 1961 lle June 22, 1965 w. J. ANDERSON ELECTRICAL MUSICAL INSTRUMENT 2 Sheets-Sheet 2 Filed Nov. l5, 1961 t .vm

United States Patent Orifice 3,190,951 Patented June 22, 1965 3,190,951 ELECTRICAL MUSICAL INSTRUMENT Walter J. Anderson, Elgin, Ill., assignor'to Chicago Musical Instrument C0., Lincolnwood, Ill., a corporation of Illinois Filed Nov. 1s, 1961, ser. No. 153,255 11 Claims. (Cl. SLI-1.23)

This invention relates generally to electrical musical instruments, and more specically to an improved circuit for producing solo tones.

This application is a continuation-in-part of my copend ing application of the same title, filed July 15, 1960, U.S. Serial No. 43,022, now abandoned.

Although the principles of the present invention may be included in various musical instruments, a particularly useful application -is made in less expensive electronic organs wherein the instant circuit is embodied in association with a set -of pedal keys.

In particular, when such a feature is to be embodied in an electric organ of one f the `smaller sizes, it is an important objective to minimize the quantity of structure necessary to do a satisfactory job. Accordingly, as will become apparent in reading the following description, the instant invention is readily adapted to cooperate with other structure found in such organs, and to that end employs a minimum of additional parts and obtains a number of results.

The instant invention employs a single divider stage which is selectively coupled to each of the means for producing a low register note, and to this end employs novel key-actuated means for effecting such coupling, for insuring that no more than one note at a time is so coupled when only a single key is depressed, and for providing a desired degree of sustain for such notes.

lIn solo instruments which employ a single divider to be driven from a plurality of signal sources, there is a possibility that signals from two sources will be provided at the same time. This possibility arises not only from deliberate operation, but also due to possible overlap between a sustained note and one which closely follows it. When such Va divider is provided with two signals at the same time, the operation of the divider becomes unstable, and it in turn produces a non-sonorous tone, known in the trade as burble Accordingly, it is an object of the present invention to provide an improved circuit for an electric solo instrument.

A further object of the present invention is to provide a` solo circuit for an electrical instrument .which is free of undesired background noises, notes, etc.

A still further object of the present invention is to provide a solo circuit which is adapted to sustain the various notes played after release of the playing key for a predetermined time.

Yet another object of the present invention is to provide means by which burble is avoided in an instrument of the type described.

Yet another object of the present invention is to provide a solo instrument capable of producing sustained notes which incorporates means for preventing burble if a second note is played while a first note is being sustained.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which preferred structural embodiments incorporating the 'principles of the present invention are shown .by way of illustrative example.

On the drawings: FIGURE 1 is a schematic diagram of an electrical circuit for a musical instrument provided in accordance with the principles of the present invention, a portion of this embodiment being omitted from the drawing to avoid duplication of illustration; and

FIGURE 2 is a schematic diagram of another embodiment of the invention shown in FIGURE l, that portion of the invention which is common to both embodiments being included in FIGURE 2. t

As shown on the drawings:

The principles of this invention are particularly useful when embodied in an electrical musical instrument, the circuit of which is illustrated in FIGURE l, generally indicated by the numeral 10. The instrument circuit 10 includes a plurality of tone signal generators 11 of any known type, each of which oscillates at chromatically spaced frequencies which correspond to a musical scale. The detailed `structure of the generators 11 does not form a part of the ins-tant invention, Ibut preferably comprises the lowest frequency stage of a continually oscillating frequency dividing cascade circuit, as is shown in my Reissue Patent 24,743. Such generator stages include a normally nonconducting electron-coupled readout elemen-t 12 which may be disposed within or separate from the oscillator means and `which here and in such patent comprises a plate 12 from which the preassigned frequency signal may be withdrawn for use in the solo section of the instrument.

Each generator readout element 12 is connected by a blocking capacitor C13 to a resistive output path provided by a load resistor R14, which is connected to a common collector 15 which leads toa terminal 16.

As shown in FIGURE 2, the terminal 16 .is connected to the grid of a signal amplifying tube 17 by means of a coupling capacitor C18, the opposite sides ot which are connected to a pair of load resistors R19, R20 which are grounded. A grounded source of B+ potential 21 :is connected to the plate of the signal amplifying tube 17 through a plate load resistor R22, such plate being also connected by a coupling capacitor C23 to an input terminal 24 located in a resistance-capacitance mesh of a frequency divider generally `indicated at 25 which forms a part of an electroacoustic translating system which further includes an amplifier 26 and a speaker 27.

The frequency ydividing stage 25 illustrated herein is known in the art, and is known as an Eccles-Jordan circuit, its mode of operation also being known inthe art. The divider stage 25 is a flip-dop circuit which oscillates in re-V sponse to the frequency present at the terminal 24, and which includes a tube 28 having a plate 29 serving as a normally nonconducting electron-coupled readout element which is connected through a load resistor R30 to the input of the amplifier 26. The frequency present within the tube 28 to which the readout element 29 can be coupled is one-half of that present at the terminal 24. Thus the frequency dividing cascade stage which provides the signal source of a frequency corresponding to the note C3 is effective through the frequency divider 25 to provide the note C2, and in like manner, each of the lseveral generators 11 provides a note which is suboctavely related thereto.

The frequency divider stage 25 includes the tube 28 or equivalent means which has a pair of indirectly heated cathodes 31, 31 which are connected to a source 32 of positive bias. The tube 28 further includes a pair of control grids 33, 34, to each of which a grounded biasing resistor R35 is connected. A plate 36 is connected by a resistor R37 to the terminal 24 which, in turn is connected by a load resistor R38 to a source of positive plate voltage 39, In like manner a scren grid 40, employed as a plate, is connected to the terminal 24 by a resistor R41.

capacitor C42 which is provided with a shunt resistor R43.

In like manner the screen-plate 40 is connected by a coupling capacitor C44 to the grid 34, the capacitor C44 being shunted by a resistor R45.

As brought out more fully later herein, the readout element 29 is provided with a coupling potential only when a note is being played or is being sustained, so that any stray oscillations, which might occur will not appear as background noise between the playing of individual notes.

Referring again to FIGURE 1, the means for rendering the various generator readout elements 12 and the divider readout element 29 conductive and nonconductive will be described. Broadly speaking, to this end, each of the generators 11 is provided with a playing-key operated means for controlling a number of sources of potential. A grounded source of positive coupling potential 4e` is connected to a pair of distributor leads 47, 4S. The distributor lead 47 is in turn connected to a contact 49, there being a contact 49 for each of the notes or generators. Each of the generator readout elements 12 is connected to a l-oad resistor R56? and a current limiting resistor R51 connected in series therewith to a contact 52, here illustrated as beinga movable contact. The contact 52 is illustrated in its released or non-playing position, and is mechanically coupled to the playing key so that when the playing key is actuated, the contact 52 becomes close circuited with the contact 49, by which the positive coupling potential from the source 4o is applied to the readout element 12, thereby coupling it to the generator 11. The signal thus coupled appears at the terminal 16 for halving by the divider stage 25 as described.

The closing of the contacts 49, 52 in addition to rendering the readout element 12 conductive, also applies a potential to a sustain means or storage memberV here comprising a capacitor C53, one side of which is grounded, and the other side of which is connected to the junc- C53 will continue to appear at the readout element 12,

thereby effecting a sustaining of the played note. The value of the storage member C53 is preferably so selected as to produce a Substantial period of sustained coupling, andwhere values are chosen as specified later herein for various components, the storage time or sustain time for such coupling will be about six seconds, which period begins with the release of the playing-key.

The distributor line 43 which is connected to the source of positive coupling potential 4o is also connected to a contact 54, here illustrated as being movable and mechanically coupled to the contact 52 for joint movement. The contact 54 is engageable with an additional contact 55 which is connected to a collector line 56. The distributor line 48 and the collector line 5o likewise are connected to similar contacts 54, 55 for each of the generators 11. rThe line 56 has a connection with a terminal 57, shown in both FlGURES l and 2, to which terminal 57 a positive coupling potential may thus be applied simultaneously with the rendering of the generator readout element 12 conductive for supplying positive coupling potential to the divider readout-element 29.

As best seen in FlGURE 2, a current limiting resistor R58 is connected in series with a load resistor R59 which is connected to the plate or readout element 29. (A line 6G shown in l lGURE 2 does not form a part of the ernbodiment illustrated in FlGURE 1.)

Y To the junction between the resistors R53 and R59 there is connected a grounded capacitor C60 which is a tone sustaining or storage member which becomes positively charged whenever the divider readout element 29 is rendered conductive by closing of the contacts 54, 55.V

through contacts 54, 55, the charge then on the storage member Coil will gradually discharge through the load resistor 59 to keep the divider readout element 29 conductive for a sustained period of time which preferably is shorter than that etected by the storage member C53. When electrical component values are selected corresponding to the values presented below, the storage member Cd@ will effect a tone sustaining function or divider readout element coupling for a period of about three seconds.

Referring again to FGURE 1, it will be noted that each of the contacts 52 is engageable with a Contact 61 whenever the playing-key is in a released position. To each of the contacts 61, there is connected one side ofan electronic switch or cold cathode gas discharge tube o2, the other side of the gas'tube 62 being connected by a line 63 to similar other sides of the other gas tubes. A source'of negative ignition, decoupling or bias potential 64 is connected by a distributor line 65 with a contact d6 which is jointly movable with the contacts 52, 54, and which is engageable, when moved, with a Contact 67 connected to the line 63 and hence to said other sides of the gas tubes e2. When the contacts 52, 54, 6o are simultaneously moved by actaution of the corresponding playing-key, the Contact S1-leading to the one side of the gas tube 62' is thus disconnected and the contacts 6o, 67 are closed, thereby bringing a relatively negative biasing, decoupling, or ignition potential therethrough to the line 63 for igniting all of the noncorresponding gas tubes 62, they still beingin closed circuit with their corresponding readout element 12 and storage member C53. Since the effective or relative potential at the source 64 is suicient to ignite such noncorresponding gas tubes 62, they become conductive and hence a decoupling potential of a value slightly below ground appears on the associated readout element 12 to preclude or suppress any electronic coupling between such readout element and the associated generator 11. The negative decoupling ignition or bias potential also is simultaneously applied to the corresponding storage member C53 to bring its charge near ground level, thereby effectively discharging it instantly so that if it Vwere then sustaining a note, such sustaining would be instantaneously terminated. Thus the playing-key operated means are operative when actuated to render the readout element of Vnoncorresponding generators instantly nonconductive, as well as to cancel any coupling charge ron the noncorresponding generator sustain members; the playing-key operated means is further operative when in the non-actuated position and any other such playingvkey operated means is actuated, to coact in effecting instantaneous termination or suppression of the corresponding generators signal in response to the decoupling potential applied thereto. Thus when one of the thirteen keys of the instant embodiment is actuated, all gas tubes Yexcept the corresponding one are ignited to bias the noncorresponding readout elements with a non-coupling potential and to eiect a disabling discharge of their sustain members to terminate any readout then occurring, and to preclude any other stray coupling.

Preferably a source of positive bias potential 68 is also provided and is connected to the line 63 by means of a coupling resistor R69 which provides aV series impedance therebetween. It is an inherent characteristic of typical generators 11 that some positive potential will be present at the readout element 12, for example about titty volts. However, the cathode is maintained more positive by a source l11a to'render the readout element 12 normally nonconducting. Thus any voltage on the element 12 is Vconducted by the Contact 52 to the Contact 61 and appears .as is typical for commercial gas tubes. Thus an effective net voltage drop across the non-ignited gas tube 62 of about twenty volts will be present rwhere the bias voltage is seventy volts, which voltage drop or diierence is such that the gas tube 62 is biased well away `from its ignition potential. `However, when the ignition potential is :applied by closing of the contacts 66, 67, the impedance R69 permits the positive bias potential to be readily overpowered to cause a current flow to discharge or slightly negatively charge the capacitor C53, any negative charge ion which is quickly reversed when the corresponding playing-key operated means is actuated.

By the addition of certain components presently to be described, the switch elements incorporating the contacts 66, 67 may be omitted. Such an embodiment is illustrated in FIGURE 2 wherein like numerals or reference characters have been used to identify components identiica-l to those described in FIGURE l. The collector line 56 communicates through a series-connected blocking diode 73 with the terminal 57 by means of the lead 60 and is also connected to a'control grid 77 of an electronic switch tube 70 through a conductor 78 by means of a preferablyeincluded current-limiting Vand voltage-dividing resistor R81. A plate 74 of the tube 70 is connected to the line 63 and hence normally has a positive biasing potential applied thereto. The cathode 75 of the tube 70 is connected to a source of negative ignition or bias potential 76. In order to suppress cathode-plate current therein, the grid 77 thereof is provided with a connection through 4a ybiasing resistor R72 to a source of lstrong negative bias potential 71, the potential present at the source 71 being greater than the potential present at the source 76 for such purpose. When the contacts S4, 55 of any one of the playing-key operated means are closed, the negative blocking bias is overcome by the potential of the source 46 to render the electronic switch 70 conductive, thereby allowing the source of negative ignition, decoupling, or bias potential 76 to overpower the source of positive potential 68 to ignite all the gas tubes 62 except the corresponding one as described before. If desired, a capacitor C79 may be provided between the lead 60 and ground to cooperate in the provision of a noise free circuit.

It is to be understood that frequencies and values of voltage, resistance, and capacitance which are disclosed herein are exemplary, and have not been presented by way of limitation. It is apparent that if longer or shorter sustain times were desired, corresponding changes in circuit parameters would be required. It is also apparent that if gas tubes 62 having a diiTerent ignition potential were employed, suitable allowance, for example in ignition voltages, would be required.

Values for the resistances and capacitances that have given desired results are:

C13 mfd .0015 C18 Infd-- .01 C23 mfd .01 C42 mid .0005 C44 mfd-.. .0005 C53 mid .22 C60 mfd-- .22 C79 rnfd..- .0l R14 ohms 1,500,000 R19 do 47,000 IR20 do 2,200,000 R22 do 100,000 R30 do 1,500,000 R35 a do 500,000 R37 1 do 100,000 R38 1 do 47,000 R41 do 100,000 vR43 d0 500,000 R45 do 500,000 R50 do 22,000,000 R51 do-- 22,000 R58 do 22,000

6 R59 ohrnsnl 1,500,000 R69 do 47,000 R72 do 47,000 R01 do... 10,000

It is to be further understood that the disclosed voltage values and polar-ities are relative to each other. For example, the voltage on a nonconducting readout element can be `raised provided that its voltage value is less than that of the cathode. With this principle in mind, it is within the concept of my invention that the voltage value of the source of decoupling potential 64 could be raised 70 volts to ground, that ground could be raised to +70 volts, that the source of bias potential 68 could be raised to volts, and that the coupling voltage could be raised to +220 volts, etc. In other Words, all voltage values could be selected with respect to a different reference point. By referencing all voltage values with respect to the most negative disclosed circuit point, the invention may be constructed with only positive sources of voltage.

Although various minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody Within the Iscope of the patent warranted hereon all such embodiments as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. In an electrical musical instrument:

(a) a plurality of tone signal generators;

(b) each individual generator having an output path and a normally nonconducting electron-coupled type of readout element connecting the generator to said path;

(c) a common collector to the which the output paths from said generators are connected;

(d) an electroacoustic translating system coupled to said common collector;

(e) a playing-key operated means for each individual generator and connected to said readout element thereof, said means selectively rendering said readout element conductive while the key is actuated and for a sustained period of time beyond key release; and

(f) a gas tube means for each individual generator and being under the control of said playing-key operated means and operative by ignition to directly render said readout element nonconductive instantly in response to playing of corresponding playing-key operated means of any other generator during said sustained period.

2. In an electrical musical instrument:

(a) a plurality of tone signal generators; (b) each individual generator having an output path and a normally nonconducting electron-coupled type of readout element connecting the generator to said path;

(c) a common collector to the which the output paths from said generators are connected;

(d) an electroacoustic translating system including a frequency divider coupled to said common collector, said frequency divider having a normally nonconducting electron-coupled type of readout element incorporated therein; and

(e) a playing-key operated means for each individual generator and connected to said readout element thereof, said means selectively simultaneously rendering conductive the individual readout element thereof and the readout element of said translating system While the key is actuated and for a sustained period of time beyond key release, said means being operative to directly render the individual readout element instantly nonconducting in responseto playing of corresponding playing-key operated means of any other generator during said sustained period.

3. In an electrical musical instrument:

(a) a plurality of tone signal generators;

(b) each individual generator having an output path and a normally nonconducting electron-coupled type of readout element connecting the generator to said path; t

(c) a common collector to the which the output paths from said generators are connected;

(d) an electroacoustic translating system coupled to said common collector;

(e) playing-key operated means for each individual generator, said means selectively rendering conductive the individual readout element thereof;

(f) a separate storage member for each individual generator, in circuit With the readout element thereof, and chargeable in response to playing of the corresponding playing-key operated means, and operative on said readout element While so charged to effect continuation of the signal conduction by the individual readout for a period of time after release of the playing-key operated means;

(g) said playing-key operated means including means under the control of other of said playing-key operated means for reversely charging the corresponding separate storage member instantly while the key is unactuated.

4. In an electrical musical instrument:

(a) a plurality of tone signal generators;

(b) each individual generator having an output path and a normally nonconducting electron-coupled type of readout element connecting the generator to said path;

(c) a common collector to which the output paths from said generators are connected;

(d) an electroacoustic translating system coupled to said common collector;

(e) a source of coupling potential;

(f) playing-key operated means for each individual generator, said means selectively connecting said source of coupling potential to the corresponding readout element to for rendering it conducting;

(g) a source of bias potential of a magnitude and polarity that will render the readout element nonconducting; and

(h) an electronic switch means for each generator connected through the playing-key operated means to the corresponding readout element and connected through a noncorresponding playing-key operated means to said source of bias potential, and operative to couple said source of bias potential to said corresponding readout element in response only to playing of said noncorresponding playing-key operated means, each readout element being thereby biased to a nonconducting state by the playing of said noncorresponding playing-key operated means.

5. In an electrical musical instrument:

(a) a plurality of tone signal generators each having and electron-coupled type of readout element;

(b) Van electroacoustic translating system;

(c) a common collector -connecting all of said readout elements to said translating system;

(d) a source of coupling potential and a source of decoupling potential; and

(e) playing-key operated means operative When actuated to connect said source of coupling potential to a selected one of the readout elements for effecting playing of its tone signal, said means being also simultaneously operative in response to the playing actuation to connect said source of decoupling potential to all other of said generator readout elements for effecting suppression of their respective tone signals.

6. In an electrical musical instrument:

(a) a plurality of tone signal generators each having and electron-coupled type of readout element;

(b) an elcctroacoustic translating system;

(c) a common collector connecting all of said readout elements to said translating system;

(d) a source of coupling potential;

(e) a source of decoupling potential;

() playing-key operated means operative to connect the source of coupling potential to a selected one of the treadout elements for effecting playing of its tone signal; and

(g) a separate gas tube of each of the readout elements,

.and operative when ignited to connect the source decoupling potential thereto to preclude playing of the corresponding tone signal;

(h) said playing-key operated means for each generator being also operative during said playing to ignite the gas tube of all noncorresponding non-played readout elements.

7. YIn an electrical musical instrument:

(a) a plurality of tone signal generators each having an electron-coupled type of readout element;

(b) an electroacoustic translating system;

(c) a common collector connecting all of said readout elements to said translating system;

(d) a source of coupling potential and a source of decoupling potential;

(e) playing-key operated means operative when actuated to connect the source of coupling potential to a selected 4one of the readout elements for effecting playing of its tone signal;

(f) each of said playing-key operated means including a separate storage member in circuit with the corresponding readout element and chargeable in response to playing of the playing-key operated means and operative on such readout element to eect continuation of the coupling of the individual readout element Y for a period of a plurality of seconds after release of the playing-key operated means; and

(g) a plurality of separate gas tubes, respectively connected to one of the readout elements and its storage member, and operative during said period when ignited to instantly operatively discharge said storage member to terminate any readout element coupling and to recharge said storage member by connecting said source of decoupling potential thereto to suppress any tone signal;

(h) said playing-key operated means for each generator being also operative when actuated to ignite the gas tube of all noncorresponding readout elements Whose playing-key operated means are released.

3. In an electrical musical instrument:

(a) a plurality of tone signal generators each having an electron-coupled type of readout element;

(b) an electroacoustic translating system;

(c) a common collector connecting all of said readout elements to said translating system;

(d) a source of coupling potential and a source of decoupling potential; and

(e) playing-key operated means operative when actuated to connect said source of coupling potential to a selected one of the readout elements for effecting playing of its tone signal, said means being also simultaneously operative to connect said source of decoupling potential to all other of said generator readout elements, Whose playing-key operated means are not then operated, for effecting suppression of their respective tone signals, each of said means having a portion which is close circuited only While released for enabling connecting the source of decoupling potential to the corresponding readout element in response to actuation of another of said means.

9. In an electrical musical instrument:

(a) a plurality of tone signal generators each having an electron-coupled type of readout element on which a D.C.-potential normally appears from the corresponding generator;

(b) an electroacoustic translating system;

(c) a common collector connecting all of the generator readout elements to said translating system;

(d) a plurality of separate gas tubes, one side of each gas tube being normally connected to one of the readout elements;

(e) a source of bias potential of a polarity and magnitude substantially like that of said D.C.potential;

(f) the other side of each gas tube being connected to the source of bias potential;

(g) a source of coupling potential;

(h) a source of decoupling ignition potential; and

(i) playing-key operated means operative when actuated to disconnect said one side of the corresponding gas tube and to connect said source of potential to the corresponding readout element for coupling it to the translating system, and also operative to connect said source of decoupling ignition potential to said other side of all the noncorresponding gas tubes whose playing-key operated means are not then actuated, to overpower said bias potential and thereby to preclude any coupling of their corresponding readout elements to the translating system.

10. In an electrical musical instrument:

(a) a plurality of tone signal generators each having a normally nonconducting electron-coupled type of readout element connected to an output path on which readout element a D.C.potential normally appears from the corresponding generator;

(b) a common collector connecting all of the output paths together;

(c) an electroacoustic translating system including a frequency divider coupled to said common collector;

(d) said frequency divider having a normally nonconducting electron-coupled type of readout element incorporated therein;

(e) a plurality of chargeable tone sustaining members each coupled to one of said readout elements;

(f) a plurality of separate gas tubes, one side of each being normally connected to one of the generator readout elements;

(g) a source of bias potential, of a polarity and magnitude substantially like that of said D.C.potential, connected to the other side of said gas tubes;

(h) a source of decoupling potential of a magnitude above that of the ignition voltage of said tubes;

(i) a source of coupling potential; and

(j) playing-key operated means operative when actuated to disconnect said one side of the corresponding gas tube and to connect said source of coupling potential to the corresponding generator readout element and tone sustaining member, and to said divider readout element and its tone sustaining member, and also operative to simultaneously therewith to connect said source of decoupling potential to said other side of all the noncorresponding gas tubes whose playingkey operated means are not then actuated to overpower said bias potential, suppress any coupling, and discharge the tone sustaining member thereof.

11. In an electrical musical instrument:

(a) a plurality of tone signal generators each having an electron-coupled type of readout element;

(b) an electroacoustic translating system;

(c) a common collector connecting all of said readout elements to said translating system;

(d) a plurality of separate gas tubes, one side of each being normally connected to one of said readout elements, and the other side of each being connected together;

(e) a source of decoupling potential having an effective voltage above that of the ignition voltage of said tubes;

(f) a source of coupling potential;

(g) an electronic switch responsive to said coupling potential and operative to connect said source of decoupling potential to said other side of said gas tubes; and

(h) playingkey operated means each operative when actuated to disconnect said one side of the corresponding gas tube, and to connect said source of coupling potential to the corresponding generator readout element, and to simultaneously render said electronic switch conductive;

(i) said electronic switch being adapted to eiect igniting of all the noncorresponding gas tubes whose playingkey operated means are not then actuated to thereby preclude coupling of their corresponding readout elements.

References Cited bythe Examiner UNITED STATES PATENTS 2,811,069 10/57 Faulkner 84l.26 X 2,811,887 1l/57 Anderson 84-1.0l 2,823,310 2/58 Anderson 84-126 X ARTHUR GAUSS, Primary Examiner.

CARL W. ROBINSON, Examiner. 

2. IN AN ELECTRICAL MUSICAL INSTRUMENT: (A) A PLURALITY OF TONE SIGNAL GENERATORS; (B) EACH INDIVIDUAL GENERATOR HAVING AN OUTPUT PATH AND A NORMALLY NONCONDUCTING ELECTRON-COUPLED TYPE OF READOUT ELEMENT CONNECTING THE GENERATOR TO SAID PATH; (C) A COMMON COLLECTOR TO THE WHICH THE OUTPUT PATHS FROM SAID GENERATORS ARE CONNECTED; (D) AN ELECTROACOUSTIC TRANSLATING SYSTEM INCLUDING A FREQUENCY DIVIDER COUPLED TO SAID COMMON COLLECTOR, SAID FREQUENCY DIVIDER HAVING A NORMALLY NONCONDUCTING ELECRON-COUPLED TYPE OF READOUT ELEMENT INCORPORATED THEREIN; AND (E) A PLAYING-KEY OPERATED MEANS FOR EACH INDIVIDUAL GENERATOR AND CONNECTED TO SAID READOUT ELEMENT THEREOF, SAID MEANS SELECTIVELY SIMULTANEOUSLY RENDERING CONDUCTIVE THE INDIVIDUAL READOUT ELEMENT THEREOF AND THE READOUT ELEMENT OF SAID TRANSLATING SYSTEM WHILE THE KEY IS ACTUATED AND FROM A SUSTAINED PERIOD OF TIME BEYOND KEY RELEASE, SAID MEANS BEING OPERATIVE TO DIRECTLY RENDER THE INDIVIDUAL READOUT ELEMENT INSTANTLY NONCONDUCTING IN RESPONSE TO PLAYING OF CORRESPONDING PLAYING-KEY OPERATED MEANS OF ANY OTHER GENERATOR DURING SAID SUSTAINED PERIOD. 